1. Field of the Description
The present description relates, in general, to prismatic actuators, and more particularly, to a prismatic parallel elastic mechanism for use in robot-environment interaction tasks, such as moving a support load such as a robot with a hopping motion (e.g., a translational elastic actuator used in a “hopping robot”).
2. Relevant Background
Legged robots have been in wide use for many years and have many varying designs. For example, hopping robots are one type of design for legged robots or machines. Hopping robots are highly dynamic mobile platforms that have proven to be useful in many applications and environments. More recently, control and simulation of hopping robots has been simplified by representing these robots with reduced-dimensional models.
However, an ongoing challenge with the design of a hopping robot is that these robots require high speed and high force actuation due to the need to achieve non-trivial ground clearance to generate the hopping motion. In one exemplary design, a quadruped robot was constructed that could walk and also hop robustly using hydraulic actuators. Other designs have been proposed and researched that have achieved hopping motions with monopod, biped, and quadruped robots using electrical motors.
Untethered, hydraulically-actuated hopping robots can often outperform their electrical motor counterparts, but such hopping robots cause safety concerns for broader use outside the research environment and also present added design constraints. Hydraulic actuators in a robot system are powered by a compressor, which is typically large and heavy and which is most often placed on the body of the robot making the whole robot heavier than desired and bulky to implement. Further, compressors may operate at high pressures, be fueled by flammable liquids, and drive very large actuator forces. Each of these operating characteristics of a compressor poses safety hazards to human operators, especially during legged locomotion where collisions (wanted or unwanted) can be ubiquitous.
Some legged (but non-hopping) robots have also been designed that employ series elastic actuators (SEAs) to drive their rotary joints. By introducing compliance between the actuator and the robot linkage, an SEA is capable of storing energy and absorbing impacts between the robot and the environment. On the other hand, parallel elastic actuators (PEAs) can reduce power consumption and increase the net force or torque of the actuator during legged locomotion. Despite these advantages, few prismatic (translational motion) PEAs have been implemented due, in part, to the difficulties in converting the rotary motion of a typical electric motor to linear movement, which can introduce unacceptable friction, hysteresis due to gearing backlash, and non-linear force output.
Hence, there remains a need for an improved design for a hopping robot actuator mechanism. Particularly, there is a growing need for a prismatic actuator that can be used to replace the effective but very bulky and, in some cases, unsafe hydraulic actuators presently in use in many hopping robots.